Kraken\Event\BaseEventEmitterTrait::findListener PHP Method

    public function findListener($event, callable $listener)
    {
        $listeners = isset($this->eventListeners[$event]) ? $this->eventListeners[$event] : [];
        foreach ($listeners as $index => $eventListener) {
            if ($listener === $eventListener->getHandler()) {
                return $index;
            }
        }
        return null;
    }